Integrated circuit devices have been subject to increasing susceptibility to damage from the application of excessive voltages, for example, by electrostatic discharge (ESD) events. This susceptibility is due, in large part, to the decreasing gate oxide thicknesses, which have resulted as very large scale integration (VLSI) circuit geometries continue to shrink. In particular, during an ESD event, charge is transferred between one or more pins of the integrated circuit device and another conducting object, in a time period that is typically less than one microsecond. This charge transfer can generate voltages that are large enough to break down insulating films (e.g., gate oxides) on the integrated circuit device or can dissipate sufficient energy to cause electro-thermal failures in the integrated circuit device. Such failures include contact damage, silicon melting, or metal interconnect melting.
Bond pads on the integrated circuit die are electrically connected to the internal circuitry within the integrated circuit device. Even though the integrated circuit die is encapsulated with a protective material, these bond pads allow the integrated circuit die to be electrically exposed. Protection circuits are usually connected to all I/O bonding pads of an integrated circuit, to safely dissipate the energy associated with ESD events without causing any damage to the circuitry connected to the I/O pad. Protection circuits may also be connected to power supply pads or between power supply interconnect to prevent damage to internal circuits.
Modern consumer electronics including personal portable devices, such as cell phones, digital cameras, music players, PDA's, and location-based devices, require miniaturization as well as integration to fit shrinking physical spaces and increasing performance needs. The broad use of integrated circuit devices has made them particularly susceptible to unanticipated exposure and handling, and thus ESD exposure. ESD events, whether from humans, packaging or a system, are very dangerous to the very small integrated circuits that have become so very pervasive.
Numerous technologies have been developed to meet these requirements. Inadequate or improper protection levels have plagued many of these technologies such as grounded-gate, embedded junctions, and field oxide devices. These technologies have struggled with problems including large breakdown voltages, poor snapback performance, multi-finger turn-on, and increasing leakage.
Thus a need still remains for a protection system to ensure that the manufacturing methods provide increasing reliability and performance. In view of the ever-increasing need to save costs and improve efficiencies, it is more and more critical that answers be found to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.